Burner for liquid fuels



May 21, 1963 E. sAcco 3,090,420

BURNER FOR LIQUID FUELS Filed Dec. 19, 1960 INVENTOR.

ERNESTO SACCO United States Patent Ofiice 3,090,420 Patented May 21,1963 3,090,420 BURNER FOR LIQUID FUELS Ernesto Sacco, Via Ghilini 32,Alessandria, Italy Filed Dec. 19, 196i), Ser. No. 76,686 Claimspriority, application Italy Jan. 20, 1960 2 Claims. (ill. 158-36)Burners for liquid fuels are well known, which use particular pumps toatomize the liquid fuel and make it suitable for the combustion; inother types the combustion is preceded by the mixing of the fuel with acertain amount of compressed air.

In any burner attempts are made to reach the best conditions to get thehighest efiiciency in the combustion by suitably varying the shapes ofthe various parts and the temperature or pressure of the fuel and thecomburent.

The present invention has for its object to provide a burner havingparticular devices in the fuel injection assembly suitable to improvethe burner efficiency.

The burner for liquid fuels according to this invention is characterizedin that the liquid fuel is heated in the fuel injection assembly beforebeing mixed with compressed air to reach the most suitable temperaturefor combustion.

The burner for liquid fuels according to this invention is furthercharacterized in that the heating of the fuel is accomplished by meansof an electric resistance wound in a spiral around a pipe of refractorymaterial which surrounds the fuel piping.

The burner for liquid fuels according to this invention, is alsocharacterized in that the fuel conduit, in the portion where it issurrounded by the refractory material with electric resistance, passesthrough the last portion of the compressed air conduit to the mixer, sothat the electric resistance, besides heating the fuel, may heat the airtoo, in such a way that it favours the subsequent mixing, helps avoidany dangerous deposit of unburnt fuel on the bottom of the boiler or thelike, and betters the dissociation of the small parts of hydrogencontained in the air, with a remarkable increase in the thermal result.

The burner for liquid fuels according to this invention, is alsocharacterized in that the necessary turbulence within the mixer isobtained by a circular ring distributor of air, with various bores inits circumference, such bores being placed tangentially to it, so as tooblige the air to a rotatory motion.

The burner for liquid fuels according to this invention, is finallycharacterized in that the amount of fuel, coming out of the burner isregulated by means of a stiff rod passing through the last portion ofthe conduit, said rod having a longitudinal motion which may beregulated by a handle actuating a screw die system connected to an endof the rod; the other end being shaped in such a way as to be able topartially or totally interrupt the feeding of the fuel into the mixer.

An embodiment of the burner according to this invention is shownschematically and by way of example only. in the accompanying drawingsin which:

FIG. 1 is a perspective view of the longitudinal section of the lastportion of the ducts, for the comburent air and fuel, forming chambersof the ignition assembly;

FIG. 2 is an enlarged fragmentary longitudinal section of the mixtureand turbulence chambers taken on line 22 of FIG. 3; and

FIG. 3 is a section taken on line 33 of FIG. 2 and looking in thedirection of the arrows.

With reference to the drawings, 9 denotes the collection chamber of thecompressed air which from said chamber passes on through conduit 10 tothe annular distributor integral with atomizer 19 which is fastened,

by means of a stop nut 11, to a threaded element 30, which is screwed onconduit 10 and locked by a backnut 23. A shaft 15 acts on the opening ofa frustoconical element 31 arranged on the end of a fuel duct 21.Numeral 32 denotes the tangential bores of the annular distributor 22and 14 a pipe of a refractory material carrying an electric resistancewound as a double spiral 26 and 26', joined at end 33 and connected tothe electric plug pin 34 and 34' at the other end respectively.

The liquid fuel, heated in a known manner, is introduced under pressurealso in a known manner, into conduit 21; around said conduit is arrangedthe electric resistance wound on a double spiral 26 and 26'. Said twospirals are coaxial and wound with equal turns but out of phase by halfa pitch, so that the turns of one fall between the turns of the other;said spirals are welded together at the ends 33 directed towards themixer and are passed through by the electric current coming in at theplug 34 and out from the plug 34', said two plugs being located at theaccessible end of the conduit. The electric resistance heats further thefuel passing inwardly until it reaches the critical temperature, withthe consequent forming of gas which passes out, from the frustoconicalelement 31 screwed on the end of duct 21, to a degree controlled byadjustment of the stiff, control shaft 15.

The compressed air in chamber 9 passes on to conduit 10 reduced to athin cylindrical film which is heated by contact with the electricresistance 2626' as well as by radiation and then reaches distributor22. From said distributor, through the tangential bores 32, it entersthe mixing chamber inside part 22 where it is rotated at a high speedand mixed with the vaporized fuel, and forms an atomized mixture whichexits out of the burner through the bore 19.

Said mixture, being at a high temperature, on entering the combustionchamber, in which too there is a high temperature, burns quickly andcompletely, avoiding the formation of unburnt residues.

During the period of ignition of the burner, that is when thetemperature of the combustion chamber is low, the mixture on enteringthe said combustion chamber cools for the difference in temperature;said cooling, however, owing to the speed at which the mixture burns, isnot sufiicient to bring the mixture below the ignition temperature, sothat it burns without forming unburnt residues.

The comburent air has a certain degree of humidity which allows adissociation between hydrogen and oxy gen, which are then recombined inthe later combustion inside the flame, increasing the heat value of theflame and promoting a complete combustion of the fuel; said increase inthe heat value of the flame being obtained at the expense of the heatingelectric energy supplied through resistance 26, 26'.

The electric energy supplied may be calculated to pro duce a strong heatsince the air passing at a high speed through the duct 10 prevents theresistance from reaching unduly high temperatures prejudicial to itslife.

The usual cleaning of the atomizer and other parts, may be accomplishedin the following way: the stop nut 11 is loosened or removed, theatomizer-mixture chamber group is taken out, and then all the passagebores may be cleaned.

On reassembling the above device, it is necessary to take care that thefrustoconical surface of the element 31 fits perfectly the inner openingof the combustion cham her, so that the air coming from the conduit 10may be compelled to enter the mixture chamber only through the suitablebores of the ring distributor.

When the surface of the element 31 does not fit per- 3 fectly theopening of said chamber, it is necessary to loosen the backnut 23, torotate the element 30 on which it is threaded, making the said elementdisplace for the distance necessary for the above fitting, and then thebacknut 23 and the stop nut 11 may be locked again.

Although for describing reasons the present invention has been describedand illustrated according to what is above stated, many modificationsand changes may be made in embodying the invention, as for instance byreplacing the stiff rod 15 and the handle 8 with suitable shut-oftvalves on the air and fuel pipings for a better regulation. All theseand other changes however, have to be considered as based on the mainideas of the invention as summarized in the following claims.

What I claim is:

1. A liquid fuel injecting assembly comprising an inner fuel ductsurrounded by an outer gas duct coaxial therewith in their last portionbefore a combustion chamber of a burner, a tube of refractory materialbetween said ducts and adherent to the fuel duct, said tube having anouter diameter slightly smaller than the inner diameter of the air duct,so as to leave an annular space of small thickness for the passage ofgas, said tube having an electric resistance coiled on its outer surfacearranged to heat the gas within the gas duct to a high temperaturedirectly by conduction and radiation and simultaneously to increase thetemperature of the liquid fuel by conduction through the Wall of saidfuel duct so that the fuel passes to a vapor phase, an annular chamberat the end of the gas duct surrounding a mixing chamber at the end ofsaid fuel duct, small radial channels provided in the walls of saidmixing chamber to permit entry of gas under pressure from said annularchamber,

means for regulating the entry of fuel from said fuel duct to the mixingchamber, and a discharge bore in said mixing chamber having a relativelysmall diameter to impart a high speed to the mixture of gas and fueldischarged into an adjacent combustion chamber.

2. A liquid fuel injection assembly according to claim 1 wherein saidelectric resistance comprises two sets of spirals exactly equal but outof phase by half a pitch so that the turns of one are arranged betweenthe turns of the other, the spiral ends being close to said mixingchamber at the discharge end of the assembly and welded to each other,and the other ends of said spirals being connected to electric plug inpins provided at an intermediate zone of said gas duct.

References Cited in the file of this patent UNITED STATES PATENTS482,508 Harvey Sept. 13, 1892 1,537,687 Morris May 12, 1925 1,779,849Lusk Oct. 28, 1930 2,225,869 Janitschek Dec. 24, 1940 2,306,831 ProctorDec. 29, 1942 2,355,693 Aldrich Aug. 15, 1944 2,424,440 Duffy July 22,1947 2,507,464 De Andrade So May 9, 1950 2,556,047 Stanley June 5, 19512,825,398 Clarke Mar. 4, 1958 FOREIGN PATENTS 469,059 Great Britain July19, 1937 250,416 Italy Oct. 5, 1926

1. A LIQUID FUEL INJECTING ASSEMBLY COMPRISING AN INNER FUEL DUCTSURROUNDED BY AN OUTER GAS DUCT COAXIAL THEREWITH IN THEIR LAST PORTIONBEFORE A COMBUSTION CHAMBER OF A BURNER, A TUBE OF REFRACTORY MATERIALBETWEEN SAID DUCTS AND ADHERENT TO THE FUEL DUCT, SAID TUBE HAVING ANOUTER DIAMETER SLIGHTLY SMALLER THAN THE INNER DIAMETER OF THE AIR DUCT,SO AS TO LEAVE AN ANNULAR SPACE OF SMALL THICKNESS FOR THE PASSAGE OFGAS, SAID TUBE HAVING AN ELECTRIC RESISTANCE COILED ON ITS OUTER SURFACEARRANGED TO HEAT THE GAS WITHIN THE GAS DUCT TO A HIGH TEMPERATUREDIRECTLY BY CONDUCTION AND RADIATION AND SIMULTANEOUSLY TO INCREASE THETEMPERATURE OF THE LIQUID FUEL BY CONDUCTION THROUGH THE WALL OF SAIDFUEL DUCT SO THAT THE FUEL PASSES TO A VAPOR SURROUNDING A MIXINGCHAMBER AT THE END OF THE GAS DUCT SURROUNDING A MIXING CHAMBER AT THEEND OF SAID FUEL DUCT, SMAL RADIAL CHANNELS PROVIDED IN THE WALLS OFSAID MIXING CHAMBER TO PERMIT ENTRY OF GAS UNDER PRESSURE FROM SAIDANNULAR CHAMBER, MEANS FOR REGULATING THE ENTRY OF FUEL FROM SAID FUELDUCT TO THE MIXING CHAMBER, AND A DISCHARGE BORE IN SAID MIXING CHAMBERHAVING A RELATIVELY SMALL DIAMETER TO IMPART A HIGH SPEED TO THE MIXTUREOF GAS AND FUEL DISCHARGED INTO AN ADJACENT COMBUSTION CHAMBER.